In general, in order to test electrical properties of a device to be tested, stable electrical coupling between the device to be tested and a test device should be established. Typically, a test socket is used as a coupling unit between the device to be tested and the test device.
Such a test socket couples a terminal of the device to be tested to a pad of the test device and enables electrical signals to flow in both directions. To this end, an elastic conductive sheet or a spring pin is used as a contact unit that is used in the test socket. Such an elastic conductive sheet connects an elastic conductive unit to the terminal of the device to be tested, and since the spring pin has a spring therein, it ensures smooth coupling between the device to be tested and the test device, it may mitigate a mechanical shock that may occur when coupling is performed, and thus it has been used for most test sockets.
As an example of the test socket, a test socket 20 shown in FIG. 1 includes a conductive silicon unit 8 that is in contact with a terminal 4 of a ball grid array (BGA) semiconductor device 2, and a dielectric silicon unit 6 that is not in contact with the terminal 4 of the semiconductor device 2 to be able to support the conductive silicon unit 8 and functions as a dielectric layer. A ring-type conductive ring 7 is disposed on the upper surface of the conductive silicon unit 8 that electrically couples a contact pad of a socket board 12, which performs a test on the semiconductor device 2, to the terminal 4 of the semiconductor device 2
The test socket is efficient in a test system that presses several semiconductor devices to establish electrical contact, each of its conductive silicon units is independently pressed, it is easy to match with the flatness of a peripheral apparatus, and thus it is possible to enhance its electrical properties. In addition, since the test socket prevents the conductive silicon unit of a metal ring from becoming spread when being pressed by the lead terminal of the semiconductor and minimizes displacement, it has a characteristic in that life of a contactor is extended.
A test socket of FIG. 2 disclosed as another typical example includes, by a plating, etching, or coating technique, a conductor 22 on the upper and lower surfaces of the conductive silicon unit 8 that electrically couples the contact pad 10 of the socket board 12 performing a test on the semiconductor device 2 to the terminal 4 of the semiconductor device 2.
According to the typical test socket described above, since the rigid conductor 22 is disposed on the upper and lower surfaces of the completed conductive silicon unit by the plating, etching, or coating technique, the elasticity of a contact unit decreases as compared to the silicon unit without the conductor. Thus, advantages of an integrated silicon contactor that is intended to be in elastic contact with the terminal of the semiconductor device and a pad of a test board decrease, and due to frequent contacts, it has limitations in that a plated, etched, or coated surface, and the terminal of a counterpart semiconductor device or the pad of the test board are damaged and a foreign material may enter.
In order to solve these limitations, a test socket as shown in FIG. 3 is disclosed. Such a test socket includes a conductive silicon unit 8 that is in contact with the terminal 4 of the BGA semiconductor device 2 and that is formed by mixing silicon with conductive metallic powder; and a dielectric silicon unit 6 that is not in contact with the terminal 4 of the semiconductor device 2 to be able to support the conductive silicon unit 8 and functions as a dielectric layer. In this case, one or both of an upper part or a lower part of the conductive silicon unit 8 has conductive reinforced layers 30 with higher density than that of the conductive powder of the conductive silicon unit 8. Such a test socket as shown in FIG. 3 has an effect of enhancing conductivity.
However, such a typical technology has the following limitations.
While conductivity is enhanced by the conductive reinforced layer, the conductive reinforced layer may be easily deformed or damaged in frequent contact processes with the terminal of the semiconductor device 2 since it protrudes from the upper part of the conductive silicon unit. In particular, due to frequent contacts with the terminal, the protruding conductive reinforced layer may be damaged and may not maintain its appropriate shape.